The TCEQ issued the permit in January 2011 for the 1,320-megawatt plant — which would power 650,000 homes by burning petroleum coke, a coal-like oil refinery byproduct — despite calls from federal regulators to delay approval of the controversial request.

In a letter to attorneys involved in the case, Yelenosky said the permit failed to meet new federal limits for sulfur dioxide and nitrogen dioxide and did not adequately account for the millions of tons of petroleum coke that will be dumped, piled and moved on site to feed the power plant's main boilers.

“Here, the worst-case scenarios factually and legally were not modeled,” Yelenosky wrote.

TCEQ spokesman Terry Clawson on Tuesday said the agency maintains that its technical review and the issuance of the permit met the state's rules and would be protective of public health and the environment.

Officials with Houston-based Chase Power Development, the project's developer, said they did not agree with elements of the ruling and considered the opposition “disingenuous.”

“If they are successful, the outcome will be overall environmentally inferior, miss-out on an important recycling opportunity and increase costs to consumers,” Rogers Herndon, chief investment officer wrote in an email.

Environmentalists, meanwhile, welcomed the judge's findings, saying the power plant, if built, would cause more problems for a city that already ranks among the state's most polluted and experiences higher than average rates for asthma and birth defects.

“The bottom line is that this power plant, as it is currently designed and planned, is simply too dirty, and would pollute the air in an area that is already overburdened with air pollution,” said Ilan Levin, an Austin attorney representing the Sierra Club, which sued the TCEQ to block the project. “So if Las Brisas wants to get a valid air pollution permit, they have to do a lot more work to develop a much cleaner project.”